Earthing switches

ABSTRACT

Earthing switch, of which the movable switching contact is normally driven by a piston and is also coupled with a nonselfbraking screwed rod, by means of which the switching contact can be driven by hand, said screwed rod forming at the same time part of a locking mechanism to lock the switching contact in its end positions and of an indicator to indicate the position of the switching contact.

United States Patent [72] lnventors Rintje Boersma l-larmelen; Gijsbert Waldemar lrik, Bilthoven, both 0! Netherlands [2!] Appl. No. 67,937

[22] Filed Aug. 28, 1970 [45] Patented Dec. 14, 1971 [73] Assignee N.V. COQ

Utrecht, Netherlands [32] Priority Nov. 4, 1969 3 3 1 Netherlands [54] EAR'IIIING SWITCHES 3 Claims, 4 Drawing Figs.

52 us. Cl.

[5|] lnt.Cl ..H0lh3l/00 [50] Field of Search 200/48,

I63, I48 B [56] References Cited UNITED STATES PATENTS 3,1 7 l ,937 3/1965 McKeough ZOO/148.2

Primary Examiner-Herman J. Hohauser Attorney-Snyder and Butrum ABSTRACT: Earthing switch, of which the movable switching contact is normally driven by a piston and is also coupled with a nonself-braking screwed red by' means of which the switching contact can be driven by hand, said screwed rod forming at the same time part of a locking mechanism to lock the switching contactin its end positions and of an indicator to indicate the position of the switching contact.

PATENTED micmsn F l G. 4

AM/NE Boa-KIM A INVENTOR ATTORNEY .1 EARTHING SWITCHES The invention relates to an earthing switch comprising two fixed contacts kept space apart by an insulator, an axially movable hollow switching contact which is permanently electrically conductively connected with one of said fixed contacts and cooperates with the other fixed contact to close and to break the connection with earth, a double-acting cylinder containing a piston which is coupled with the switching rod to drive same and stop members to limit the stroke of said piston.

An earthing switch of this kind must be locked in both end positions and be provided with a reliable indication of its position and with the possibility to be switched in and switched off by hand. Moreover, when used in metal clad switchgear, such an earthing switch may occupy only little space.

The invention has for its object to provide an earthing switch which complies with these requirements and it is attained in the provision of a nonself-braking screwed rod extending in the axis of the cylinder and being supported with its one end portion rotatably in the cylinder cover at the end of the cylinder remote from the switching rod and with its other end portion both rotatably and axially slidably in a central boring of the piston and in the cavity of the switching rod connecting to said boring, members mounted in the piston and cooperating with said screwed rod as a nut, said piston and said switching rod being locked against rotation about their axes, an unround locking disc mounted on the end portion of the screwed rod projecting outwards from said cylinder cover, a movable locking member cooperating with said locking disc and a spring-loading said locking member, said locking disc and said locking member being so constructed and cooperating in such a manner as to keep the piston in each one of its two end positions forced against a stop member by the section of said spring.

The screwed rod which is positively coupled with the switching rod and is rotated during the movement of the piston and the switching rod can be used in a simple manner for locking the end positions, driving the switch by hand and the indication of the position. Since, during the axial movement of the switching rod, the screwed rod remains in place in the cylinder the device for the locking operation, the driving by hand and the indication of the position requires little additional space.

in order to drive the earthing switch by hand the end portion of the screwed rod projecting outwards from the cylinder and the side of the locking disc remote from the cylinder may be so constructed as to permit the mounting of a spanner thereon, by means of which the screwed rod can be rotated by hand to drive the switching rod.

The locking disc may be provided with marks to indicate the end positions of the piston and the switching rod.

The invention will be elucidated with the aid of the drawing. In the drawing:

FIG. I is partly an axial sectional view, partly an elevational view of an earthing switch according to the invention,

FIG. 2 is an end view of said switch,

FIG. 3 is a sectional view taken on line llllll in FIG. 1 and FIG. 4 is an elevational view of a part of a spanner for driving said switch by hand.

The earthing switch shown in the drawing is provided with two fixed contacts 2 and 3 kept spaced apart by an insulator l and with an axially movable hollow switching rod 4 which is permanently electrically conductively connected with the fixed contact 2 and is adapted to be brought into and out of cooperation with the fixed contact 3 to close and to break the connection with earth. The fixed contact 3 is connected to a conductive part (not shown) of a switch plant which is accommodated in a metal envelope 5 connected to earth.

The switching rod 4 and the fixed contact 2 are supported by a metal block 6 which is attached to a cover 7 of the metal envelope 5. The switching rod, the fixed contact 2, the block 6, the cover 7 and the envelope 5 are all metallically interconnected, so that they all have earth potential.

Provided in the block 6 is a double-acting cylinder 8 containing a piston 9 which is attached to the switching rod 4. The stroke of the piston and also that of the switching rod are limited by stop members 10, 11. The cylinder spaces 1'2, 13 are in open communication with chambers provided in valve housing l8, 19 through annular chambers l4, l5 and passages l6, 17. A sectional view of one of said valve housings l8, 19 is shown in H6. 3.

it appears from FIG. 3 that the valve housing 18 is provided with a chamber 20 connecting to the passage 16 and that said chamber can be connected by means of a valve 21 either with the atmosphere through a passage 22 or with a cylinder space 24 through an opening 23. The valve 21 is secured to a piston. 25 mounted for movement in the valve housing 18 and loaded by a spring 26. Said piston 25 separates the cylinder space 24 from a cylinder space 27. The cylinder spaces 24 and 27 are connected by passages 28, 29 with a three-way cock 30 which interconnects, in the position shown, the cylinder spaces 24 and 27 and, in its other position, breaks the connection between the cylinder spaces 24 and 27 and connects the cylinder space 27 with the atmosphere through a passage 31. The cylinder space 24 is in open communication with the switchgear space 35 enclosed by the envelope 5 and the cover 7 through passages 32, 33 and 34. Said space 35 is filled with compressed gas under high pressure, e.g. air of 20 atm. The valve 19 is provided with a similar valve system.

In each of one of the two end positions of the piston 9 the three-way cocks 30 are in the position shown in FIG. 3, so that both cylinder spaces [2, 13 are under high pressure and, consequently, the piston is under no-load. If the earthing switch must be switched in or switched off the relative three-way cock 30 is changed over, so that the cylinder space 27 of the valve housing is brought into communication with the atmosphere and the valve 21 is forced to the left, whereas the relative cylinder space 12 or 13 is connected with the atmosphere. The result thereof is that the piston 9 and the switching rod are driven to the other end position by the pres sure obtained in the other cylinder space 13 or 12.

A nonself-braking screwed rod 36 extends in the axis of the cylinder 8. This screwed rod is rotatably supported with its one end portion in the cylinder cover 37, through which said end portion extends, and with its other end portion said screwed rod is supported both rotatably and axially slidably in the cavity 38 of the switching rod 4 and a central boring of the piston 9. In the cylinder 8 the screwed rod 36 has the shape of a twisted flat strip. Said strip cooperates with rollers 40 mounted for rotation about transverse pivots 39 provided in the piston 9. Said rollers 40 act as a nut mounted on the screwed rod 36. The piston 9 and the switching rod 4 are locked against rotation by means of axial rods 41 which extend through openings made in the piston and are attached to the cylinder covers. It will be obvious that, when the piston 9 and the switching rod 4 are axially moved by the pressure of the gas contained in one of the cylinder spaces l2, 13, the screwed rod 36 is rotated. The stroke of the piston 9 which is defined by the stop memberslO, 11 corresponds with a rotation of the screwed rod through an angle of about 270,as appears from FIG. 2. Conversely, when the screwed rod 36 is rotated the piston 9 and the switching rod 4 will be moved.

Mounted on the end portion 36a of the screwed rod projecting outwards from the cylinder cover 37 is an unround locking disc 42. This locking disc cooperates with a locking member in the form of a roller 43 which is provided at the free end of an arm 45 mounted on a pivot'44. The arm 45 is loaded by a spring 46.

In the switched in end position of the earthing switch the roller 43 is found on a plane part of the locking disc 42 and said roller then engages said roller in a point which is shifted slightly to the right in respect of the axis of the locking disc, so that the spring 46 will try to rotate the locking disc 42 clockwise (see FIG. 2). .The result thereof is that the piston 9 is forced with a given force against the stop member 11 through the screwed rod 36 and the rollers 40 acting as a nut,

so that theearthing switch is locked in said end position. in the switched off end position of the switch the screwed rod 36 is rotated counterclockwise through an angle of about 270 and the locking disc 42 is then positioned in the position shown in dotted lines in FIG. 2. In said position the spring 46 exerts a torque which tries to rotate the screwed rod still further in counterclockwise direction. in the said end position the piston 9 is forced against the stop member by the spring 46, so that it is also locked.

The locking disc 42 is provided with a cylindrical hub 42a and attached to the screwed rod 36 by a transverse pin 47 which projects with both ends from said hub. it is possible to mount a spanner 48 provided with studs 49 on the hub 42. These studs 49 are intended to engage the projecting end portions of the transverse pin 47, so that by means of said spanner 48 the screwed rod 36 can be rotated by hand and the earthing switch can be switched in and switched off by hand.

The locking disc 42 is provided with marks 50 and 51 which appear behind a window of a casing (not shown) enclosing the locking mechanism and thereby indicate the switched in end position and the switched off end position of the earthing switch, respectively.

What we claim is:

l. An earthing switch comprising two fixed contacts kept spaced apart by an insulator, an axially movable hollow switching contact which is permanently electrically conductively connected with one of said fixed contacts and cooperates with the other fixed contact to close and to break the connection with earth, a double-acting cylinder containing a piston which is coupled with the switching rod to drive same and stop members to limit the stroke of said piston. characterized in the provision of a nonself-braking screwed rod extending in the axis of the cylinder and being supported with its one end portion rotatably in the cylinder cover at the end of the cylinder remote from the switching rod and with its other end portion both rotatably and axially slidably in a central boring of the piston and in the cavity of the switching rod connecting to said boring, members mounted in the piston and cooperating with said screwed rod as a nut, said piston and said switching rod being locked against rotation about their axes, an unround locking disc mounted on the end portion of the screwed rod projecting outwards from said cylinder cover, a movable locking member cooperating with said locking disc and a spring loading said locking member, said locking disc and said locking member being so constructed and cooperating in such a manner as to keep the piston in each one of its two end positions forced against a stop member by the action of said spring.

2. An earthing switch according to claim 1, characterized in that the end portion of the screwed rod projecting outwards from the cylinder and the sideof the locking disc remote from the cylinder are so constructed as to permit the mounting of a spanner thereon, by means of which the screwed rod can be rotated by hand to drive the switching rod.

3. An earthing switch according to claim 1, characterized in the provision of marks on the locking disc to indicate the end positions of the piston and the switching rod. 

1. An earthing switch comprising two fixed contacts kept spaced apart by an insulator, an axially movable hollow switching contact which is permanently electrically conductively connected with one of said fixed contacts and cooperates with the other fixed contact to close and to break the connection with earth, a double-acting cylinder containing a piston which is coupled with the switching rod to drive same and stop members to limit the stroke of said piston, characterized in the provision of a nonself-braking screwed rod extending in the axis of the cylinder and being supported with its one end portion rotatably in the cylinder cover at the end of the cylinder remote from the switching rod and with its other end portion both rotatably and axially slidably in a central boring of the piston and in the cavity of the switching rod connecting to said boring, members mounted in the piston and cooperating with said screwed rod as a nut, said piston and said switching rod being locked against rotation about their axes, an unround locking disc mounted on the end portion of the screwed rod projecting outwards from said cylinder cover, a movable locking member cooperating with said locking disc and a spring loading said locking member, said locking disc and said locking member being so constructed and cooperating in such a manner as to keep the piston in each one of its two end positions forced against a stop member by the action of said spring.
 2. An earthinG switch according to claim 1, characterized in that the end portion of the screwed rod projecting outwards from the cylinder and the side of the locking disc remote from the cylinder are so constructed as to permit the mounting of a spanner thereon, by means of which the screwed rod can be rotated by hand to drive the switching rod.
 3. An earthing switch according to claim 1, characterized in the provision of marks on the locking disc to indicate the end positions of the piston and the switching rod. 